Advanced Thermophilic Fermentation of Wood Wastes with Nitrogen-rich Agricultural and Other Organic Wastes for the Production of Biomethane/Renewable Natural Gas Globally

Improved forest management comprised of the collection of tree mortalities and of the thinning of tree stands can yield a large, but as of now mostly un-utilized biomass resource that can be employed in conjunction with high in nitrogen content agricultural wastes such as animal manures to produce renewable natural gas via a biological process. The novel process mimics the well-known wood digestion to methane employed by lower termites but operating at thermophilic temperatures. The conversion process of renewable wood to green or bio-methane, designated as “Wood to Methane 3+2” consists of five (3+2) steps. The initial “3” steps of the process include (a) wood maceration to 1 mm particles, (b) aerobic hyperthermophilic (70o) hydrolysis of the homogenized mixture of wood and manure with the aid of thermophilic fungi (Humicola insolens and Sporotrichum thermophile), and (c) the anaerobic thermophilic (55oC) co-digestion of the feedstock into biogas. The final “2” steps consist of (d) the upgrade of the generated biogas into “primary” bio-methane fuel via a three-stage commercial membrane separation system along with the sequestration of the carbon dioxide, and (e) the conversion of the sequestered carbon dioxide into “secondary” bio-methane fuel with hydrogen produced by wind-powered water electrolysis in a thermophilic (55oC) anaerobic trickle bed reactor employing hydrogenotrophic archaea (Methanothermobacter thermautotrophicus). An optimally standardized, modular, industrial type plant treats annually 12,000 mt (metric tons) of wood wastes (80% TS) and 12,000 mt of suitable animal manures (10% TS) and generates 7.6 million Nm3 of primary and secondary bio-methane fuel along with bio-fertilizers amounting to 2,800 mt of green ammonia as ammonium nitrate, 1,000 mt of potassium concentrate and 3,500 mt of phosphate-rich humic soil amendment, has a negative 10,000 mt carbon dioxide footprint and requires 25 MW of wind power. The produced renewable natural gas can be employed by itself or along with green hydrogen as an advanced, renewable, negative carbon transportation fuel. The available relevant waste-wood resources globally are sufficient to supply as much as 1/5 of the world’s energy primary needs in the 2nd half of the 21st century.